We will characterize the structure, function and expression of rabbit microsomal cytochroms P-450s 1, 3b and related forms of P -450s K and L in three colonies of rabbits. These colonies represent inbred strains III/J, B/J, and selected outbred rabbits that differ phenotypically in the expression of elevated concentrations of P-450 1. Monoclonal antibodies to these enzymes will be used as specific inhibitors in order to assess the role of each member of this highly diverse family of P-450 enzymes in microsomal metabolism. Immunoquantitative techniques will be employed to estimate differences in the expression of these enzymes among untreated animals and among progeny of matings between the genetically defined strains of rabbits. Molecular cloning of cDNAs in expression vectors will be coupled with immunological characterization to provide identification of pertinent cDNA clones. These cDNAs will be used in turn to characterize the number and structure of mRNAs encoding this family of P-450 enzymes. the fusion proteins expressed in microorganisms transformed with the expression vectors containing cDNAs encoding these enzymes will be used in the development of additional monoclonal antibodies for the characterization of these P-450s. The antibodies and cDNA probes will be used to characterize heritable differences in the regulation of P-450 expression among the three colonies of rabbits and outbred animals.